I actually got "mailto:" working across all platforms.. you can see how in this thread:
To save you time, here's the important Info:
Update! This wasn't working on IOS devices, so I needed to encode the text for the subject and body AND IOS DEMANDS AN EMAIL ADDRESS!!!, like so:
I solved the mailto issue on safari IOS!!!!!!! The trick is to make sure to use browser/go to URL and NOT browser/open in new window specifically for mailto....for opening facebook or twitter pre-populated posts, you want to use browser/open in new window.